Use output ItemStack in Mincer

[cbrintnall]

I discovered this issue when trying to figure out why data components weren't getting copied during the recipe assembly phase. The issue is that the old approach loses any data components on output. The recipe assembly process provides copies of ItemStack so theres no need to copy it here (unless another mod decides to violate this).

You can see this fixes the issue here:

The Max Health: +2 comes from my mod forwarding the data component from beef -> minced beef.

I'm not sure if there were other reasons for manually copying the ItemStack here so let me know cause the alternative is copying over all the data components, but afaik that is wasted work.

[cbrintnall]

I'm also noticing that assembly returns empty items. My understanding is that assembly is what should be used for input items -> output and getResultItem() is for informational purposes without context.